Although I only visited Tierpark Hellabrunn (Munich) as non-Balkan European zoo, from photos/infos I think I mostly love how British zoos are built outside cities, with pretty big enclosures with grass and trees.
Dutch zoos seems very crowded and with a lot of concrete (wich would not be mine choice - as I would prefer simplsitic relatively big enclosures with grass/trees). German zoos seems that are too with a lot of concrete but not so like Dutch zoos looks like. Some very amazing exceptions exist in almost every country; France seems that have some very nice enclosures - like la vallée des singes (primate park) or Beauval zoo, or French enclosures for Kordofan giraffes - type on google Kordofan giraffe (because most captive Kordofan giraffes are kept in France, and in 2 Italian zoos, and some other).
Italy should have also some good naturalistic enclosures.
Attika zoological park in Greece it's not bad at all.
Praha zoo - amazing.
Portugese zoos - are quite interesting.
I watched Youtube video of one Polish zoo, can't remember wich but was very nice with wast greeny enclosures (like for giraffes).
Skopje zoo, although was awfull before some 10 years, it is now pleasant for eyes.
Animal collections are best in big countries like Germany, UK, France (or USA), and in some smaller countries like Netherlands or Czech Republic and other.